The invention relates generally to production planning, and more particularly to move target setting for a product flow in a manufacturing environment.
In processing lines for semiconductor fabrication, there are various processing stages through which wafer lots proceed to achieve a production goal specified in a master production schedule (MPS). The progress of wafer lots through a processing line is monitored for management purposes. A ‘move’ is a basic unit for calculating the progress of wafer fabrication. For example, when a wafer completes one processing stage, one ‘move’ is achieved. Typically, a monthly move target is set for a semiconductor fab, specifying a monthly goal of product moves.
Various conventional methods of move target setting have been developed to manage product flows. According to one conventional method, the move target is determined according to cycle time of product fabrication in a manufacturing system. This method uses the cycle time of the product fabrication and number of working days specified in current month MPS and next month MPS to determine a move target for products for a current month. When the cycle time exceeds the sum of working days of the current month, the MPSs of the next two months are considered in determining the move target of the current month. The conventional method focuses on the quantity of achieved moves, but ignores move targets assigned to products of different months.
According to another conventional method, achieved moves of products are calculated, and a move target thereof is determined accordingly. The achieved moves of a particular product are referred to as the “WIP energy” thereof, and may be used to estimate impact of the WIP profile on move target achievement.
Both methods focus on quantities of moves, and neglect the ‘composition’ thereof.
Ensuring quantities of moves achieve a preset target, however, cannot guarantee a corresponding delivery requirement being fulfilled. For example, a monthly move target is set as 900,000, and a daily move target is 30,000 accordingly. Monthly delivery requirement, however, may not be fulfilled when daily movement targets are achieved for each working day during the month. For example, there are two products A and B being fabricated, wherein product A is to be delivered this month, while product B is to be delivered next month. When the achieved moves are accomplished on WIPs of product B, and product A is suspended, the delivery requirement of product A may not be fulfilled although the daily move target is achieved. The “composition” of the moves is neglected conventionally, in spite of its importance.